1. Field of the Invention
The field of the invention is that of the design and production of graphic images containing information in the form of geometrical or alphanumeric symbols. For a certain number of applications, the information calculated and displayed on viewing devices must be highly reliable in that it provides vital information concerning the parameters or the correct operation of a system. Obviously worth mentioning are the transportation field, and in particular the aeronautics field, but also any industries requiring secure and reliable checks on graphic images. The images displayed are calculated from algorithms and must correspond to very precise specifications. These specifications can be identified in reference images. Hereinafter in the text, an obtained image will be called calculated image and an anticipated image will be called reference image.
2. Description of the Prior Art
Currently, the checking of an image is handled by an operator directly on a screen showing the obtained image. There are two methods for checking this image.
A first method consists, for the operator, in comparing the obtained image with its textual description. For example, a symbol X must be located at the top of the image. In this case, the text describing the elements to be observed may lead to a particular interpretation on the part of the operator checking the result. For example, if the operator has to check that the symbol X is positioned at the top of the screen, should he consider that, if the symbol X is in the top half of the screen, then it is correctly placed, or indeed should he consider that the symbol must be exactly aligned on the top edge of the screen?
A second method consists, to avoid the above interpretation errors, in producing the anticipated image in graphic form. In this case, there is no longer any possible interpretation. The obtained image must then be strictly identical to the reference image. The comparison of the two graphic formats is, these days, carried out by the naked eye. On a complex image, this method may be very tedious. We are all familiar with the “seven errors” game which consists in finding in two almost identical images the seven differences that separate them. The risks for the person in charge of the check are of:                spending huge amounts of time in searching for the differences between two images. Often, a difference of a single pixel is invisible to the naked eye and may reveal a greater problem;        not seeing all the differences between the two images and stopping at the first identified differences.        